This invention relates to fluorochemical compositions for use in providing repellent properties to a fibrous substrate material. In another aspect, this invention relates to fluorochemical compounds that contain pendent fluoroaliphatic groups proximal to one another. In yet another aspect, it relates to fluorochemical compounds that are at least in part oligomeric in nature.
The utility of organofluorine compounds as surface-active agents (i.e., surfactants) and surface-treating agents is due in large part to the extremely low free-surface energy of a C6-C12 fluorocarbon group, according to H. C. Fielding, xe2x80x9cOrganofluorine Compounds and Their Applications,xe2x80x9d R. E. Banks, Ed., Society of Chemical Industry at p. 214 (1979). Generally, the organofluorine substances described above are those which have carbon-bonded fluorine in the form of a monovalent fluoroaliphatic radical such as a perfluoroalkyl group, typically xe2x80x94CnF2n+1, where n is at least 3, the terminal part of which group is trifluoromethyl, xe2x80x94CF3.
U.S. Pat. No. 3,758,447 (Falk et al.) describes polymers that result from free radical polymerization of a monomer in the presence of perfluoroalkyl mercaptans, which act as chain-transfer agents. Mercaptans that contain pairs or triplets of closely-packed perfluoroalkyl groups are said to produce polymers with higher oil repellency levels compared with analogous polymers derived from a mercaptan with just one perfluoroalkyl group or perfluoroalkyl groups that are not closely packed.
U.S. Pat. No. 5,453,540 (Dams et al.) describes fluorochemical compositions for the treatment of textiles comprising: (i) a fluorochemical oligomeric portion comprising an aliphatic backbone with a plurality of fluoroaliphatic groups attached thereto, each fluoroaliphatic group having a fully fluorinated terminal group and each independently linked to a carbon atom of the aliphatic backbone through an organic linking group;(ii) an organic moiety (which can be functional or non-functional, and which is different from the fluorochemical oligomeric portion); (iii) a non-polymeric isocyanate-derived linking group which links the fluorochemical oligomeric portion to the organic moiety; and (iv) a group bonded thereto, which can impart soft hand, stain release, water repellency, or a durable property when the compound is applied to a fibrous substrate.
J. Polymer Science, Part A 1988, 26, 2991 (Chujo et al.) describes a di-carboxyl terminated macromonomer prepared by the free radical co-polymerization of a perfluoroalkylethyl acrylate and methyl methacrylate in the presence of thiomalic acid. Also described is the reaction of such macromonomers with organic dicarboxylic acids and organic diamines in the presence of an appropriate catalyst to afford a copolymer wherein the macromonomer is grafted onto a polyamide chain.
The treatment of hides and skins to form leather involves a number of interdependent chemical and mechanical operations. These operations may be divided into a sequence of xe2x80x9cwet endxe2x80x9d steps followed by a sequence of xe2x80x9cdryxe2x80x9d steps. A description of each of these operations is provided in Fundamentals of Leather Manufacturing, Prof Dr Heidemann (Eduard Roether KG, 1993). The primary tanning operation involves the treatment of the hide to preserve it and form useful leather. Chrome tanning salts are well known and widely used for this purpose. Chrome-tanned hides or skins are known in the art as xe2x80x9cwet blue leatherxe2x80x9d. In order to produce a uniform piece of leather with the required physical and aesthetic properties, a second tanning step, known as xe2x80x9cretanningxe2x80x9d is employed. Retanning can be accomplished using a variety of naturally derived materials including extracts from vegetables or plants, and synthetic tanning agents known as xe2x80x9csyntansxe2x80x9d, or combinations thereof. After or during retanning, the leather can be colored and fatliquored.
A number of publications have proposed various copolymers for treating leather during tanning and retanning, addressing the problem of making treated leather more water resistant or completely waterproof.
EP-A-372 746 discloses a method and process for treating leather utilizing selected amphiphilic copolymers for improving the strength, temper and water resistance of the leather. The amphiphilic copolymers are formed from a predominant amount of at least one hydrophobic monomer and a minor amount of at least one copolymerizable hydrophilic monomer. The application states that the process may be particularly useful as a one step substitute for conventional retanning and fatliquoring treatment steps.
EP-A-682 044 discloses copolymers comprising ethylenically unsaturated dicarboxylic acid anhydrides, long chain olefins and fluorolefins. Leathers treated with these polymers are shown to yield good waterproofness results according to the Bally-Penotrometer test.
U.S. Pat. No. 5,124,181 discloses copolymers which contain a) from 50 to 90% by weight of C8-C40-alkyl methacrylates, vinyl esters of C8-C40-carboxylic acids or mixtures thereof and b) from 10 to 50% by weight of monoethylenically unsaturated C3-C12-carboxylic acids, monoethylenically unsaturated dicarboxylic anhydrides, monoesters or monoamides of monoethylenically unsaturated C4-C12-dicarboxylic acids, amides of C3-C12-monocarboxylic acids or mixtures thereof as copolymerized units and which have molecular weights of from 500 to 30,000. The copolymers are used in at least partially neutralized form in aqueous solution or dispersion for making leather and furs water repellent.
WO 94/01587 discloses water-dispersible and/or water-emulsifiable co-oligomers containing (a) fatty crotonates; (b) radically copolymerizable, hydrophilic, ethylenically unsaturated acids and/or their anhydrides, and possibly (c) minor amounts of other copolymerizable comonomers. These co-oligomers are used as amphiphilic agents for greasing leather and pelts.
Despite the various publications there continues to be a need for further fluorochemical compositions for the treatment of leather to impart desired properties thereto such as water repellency, water proofness, oil repellency and stain resistance. It is further desired that such fluorochemical compositions be readily produced in a cost effective way, have sufficient storage stability and are efficient even if applied in low quantities to the substrate. Highly desired fluorochemical compositions are those that can impart both good water repellency as well as oil repellency to leather substrates. In one aspect, the present invention relates to the wet end operations which take place after primary tanning, namely retanning and fatliquoring.
This invention provides a method of treating fibrous substrates comprising contacting the fibrous substrate with a composition comprising alkylated fluorochemical oligomeric compounds comprising:
(i) a fluorochemical oligomeric portion comprising an aliphatic backbone with a plurality of pendant fluoroaliphatic groups, each fluoroaliphatic group having a fully fluorinated terminal group and each independently linked to a carbon atom of the aliphatic backbone through an organic linking group;
(ii) an aliphatic moiety having at least 12 carbon atoms; and
(iii) a linking group which links the fluorochemical oligomeric portion to the aliphatic moiety.
In another aspect, the invention provides a method of treating fibrous substrates comprising contacting the fibrous substrate with a composition comprising alkylated fluorochemical oligomeric compounds comprising:
(i) an oligomeric portion having both fluoroaliphatic and fluorine-free aliphatic pendent groups;
(ii) an aliphatic moiety having at least 12 carbon atoms; and
(iii) a linking group which links the oligomeric portion to the aliphatic moiety;
In another aspect, the present invention provides a fluorochemical leather treatment composition comprising at least one fluorochemical compound described herein. In another aspect, the present invention provides a treated substrate comprising a coating of the treatment composition on at least a portion of the substrate.
Preferably, the fluorochemical oligomeric compounds exhibit a receding contact angle, to hexadecane, of at least 30xc2x0, as defined by the test method described herein. Such compounds have improved anti-staining properties, as well as desirable oil- and water-repellent properties.
The composition comprising alkylated fluorochemical oligomeric compounds can be applied in the form of an aqueous dispersion or emulsion, or as a solution thereof in an organic solvent. The aqueous dispersions are preferred for environmental reasons. Application of the composition onto a substrate may be done by spraying, padding, roll coating, brushing or exhausting the composition onto a substrate and drying the treated substrate.
The alkylated fluorochemical oligomers in a composition useful in the invention generally contain a plurality of pendant fluoroaliphatic groups proximal to one another (e.g., located on alternating carbon atoms of an aliphatic backbone, or occasionally on adjacent carbon atoms), as distinct from isolated fluoroaliphatic groups randomly distributed throughout the compound and also as distinct from fluoroaliphatic groups uniformly located on adjacent carbon atoms.
In other preferred embodiments, the invention provides a method of treating fibrous substrates comprising contacting the substrate with fluorochemical compositions comprising fluorinated compounds of Formulas I or II
[(A)mxe2x80x94L]nRxe2x80x83xe2x80x83I
(A)m[Lxe2x80x94R]nxe2x80x83xe2x80x83II
wherein
m is 1 to 4 inclusive;
n is 1 to 4 inclusive;
each L independently comprises a linking group;
R is a saturated or unsaturated aliphatic moiety of 12 to 75 carbon atoms; and
A is a fluorochemical oligomeric portion of the formula: 
wherein
a is a number such that A is oligomeric and comprises a plurality of pendent Rf groups;
each R1 is independently hydrogen, halogen, or straight chain or branched chain alkyl containing 1 to about 4 carbon atoms;
each R2 is independently hydrogen or straight chain or branched chain alkyl containing 1 to about 4 carbon atoms;
each Q is a covalent bond or an organic linking group, such as a sulfonamidoalkylene group;
Rf is a fluoroaliphatic group, such as xe2x80x94(CF2)7CF3, that comprises a fully fluorinated terminal group;
X is a hydrogen atom or a group derived from a free radical initiator (e.g. t-butoxy).
A may further comprise a fluorochemical oligomeric portion of Formula IV: 
wherein the sum of a+b is a number such that A is oligomeric,
each R1 is independently hydrogen, halogen, or straight chain or branched chain alkyl containing 1 to about 4 carbon atoms;
each R2 is independently hydrogen or straight chain or branched chain alkyl containing 1 to about 4 carbon atoms;
Q and Qxe2x80x2 are each independently a covalent bond or an organic linking group,
Rf is a fluoroaliphatic group, such as xe2x80x94(CF2)3CF3, that comprises a fully fluorinated terminal group;
Rh is a fluorine-free aliphatic group; preferably having 6 or fewer carbon atoms.
Preferably, with reference to Formulas I and II, both m and n are one to produce an alkylated oligomeric fluorochemical of the Formulas V or VI: 
Preferably the ratio of a:b is 4:1 or more.
With reference to Formulas III to VI, it will be understood that the oligomer may have a random distribution of fluorinated and fluorine-free segments, or preferably a sequential arrangement where the oligomer comprises xe2x80x9cblocksxe2x80x9d of fluorinated and fluorine-free segments, i.e. a block copolymer. Further it will be understood that the relative position of the units derived from fluorinated monomers and fluorine-free monomers may vary with respect to the X and S moieties. In essence the following structures are both within the scope of the invention: 
As described above and further illustrated in Formulas I-VI, a fluorochemical composition useful in the invention comprises an alkylated fluorochemical oligomeric compound that generally has three principal portions: a fluorochemical oligomeric portion xe2x80x9cAxe2x80x9d, a linking group xe2x80x9cLxe2x80x9d, and an aliphatic moiety xe2x80x9cRxe2x80x9d. The fluorochemical oligomeric portion and the organic moiety are linked together by linking group L. The linking group may be a covalent bond, may result from a condensation reaction between a nucleophile, such as an alcohol, an amine, or a thiol, and an electrophile such as a carboxylic acid, ester, acyl halide, sulfonate ester, sulfonyl halide, cyanate, isocyanate, or may result from a nucleophilic displacement reaction between a nucleophile, such as previously described, and a moiety bearing a leaving group, such as the reaction between an alcohol (or alkoxide) and an alkyl halide (where the halogen atom of the alkyl halide serves as a leaving group).
Examples of suitable linking groups L include a covalent bond, straight chain, branched chain, or cyclic alkylene, arylene, aralkylene, oxy, oxo, hydroxy, thio, sulfonyl, sulfoxy, amino, imino, sulfonamido, carboxamido, carbonyloxy, urethanylene, ureylene, and combinations thereof such as sulfonamidoalkylene.
A salient component of the fluorochemical oligomeric portion is the fluoroaliphatic group, designated herein as Rf. The fluorinated compound of the invention contains a plurality of pendent Rf groups (e.g., from 2 to about 10) proximal to one another and preferably contains from about 5 percent to about 80 percent, more preferably from about 20 percent to about 65 percent, and most preferably about 25 percent to about 55 percent fluorine by weight, based on the total weight of the compound, the loci of the fluorine being essentially in the Rf groups. Rf is a stable, inert, non-polar, preferably saturated, monovalent moiety which is both oleophobic and hydrophobic. Rf preferably contains at least about 3 carbon atoms, more preferably 3 to about 20 carbon atoms, and most preferably about 4 to about 8 carbon atoms. Rf can contain straight chain, branched chain, or cyclic fluorinated alkylene groups or combinations thereof or combinations thereof with straight chain, branched chain, or cyclic alkylene groups. Rf is preferably free of polymerizable olefinic unsaturation and can optionally contain catenary heteroatoms such as divalent oxygen, or trivalent nitrogen. It is preferred that Rf contain about 35% to about 78% fluorine by weight, more preferably about 40% to about 78% fluorine by weight. The terminal portion of the Rf group contains a fully fluorinated terminal group. This terminal group preferably contains at least 7 fluorine atoms, e.g., CF3CF2CF2xe2x80x94, (CF3)2CFxe2x80x94, or the like. Perfluorinated aliphatic groups (i.e., those of the formula CoF2o+1, where o is 4 to 8 are the most preferred embodiments of Rf.
The aliphatic backbone of the fluorochemical oligomeric portion comprises a sufficient number of polymerized units to render the portion oligomeric. The aliphatic backbone preferably comprises from 2 to about 10 polymerized units (xe2x80x9caxe2x80x9d and xe2x80x9cbxe2x80x9d in Formula III to VI) derived from fluorinated monomers (i.e., monomers containing a fluorinated organic group Rf as defined above), it is more preferred that the aliphatic backbone comprise from 3 to about 8, most preferably about 4, polymerized units.
The fluorochemical compositions of the invention generally comprise mixtures of alkylated fluorochemical oligomeric compounds. Accordingly, compounds are sometimes referred to herein as having non-integral numbers of particular substituents (e.g., xe2x80x9ca=2.7xe2x80x9d). In such cases the number indicates an average and is not intended to denote fractional incorporation of a substituent. The terms xe2x80x9coligomerxe2x80x9d or xe2x80x9coligomericxe2x80x9d when used herein designate compounds containing a plurality of polymerized units, but fewer than that number of polymerized units present in a polymer (e.g., chains of 2 to about 10 polymerized units are to be considered xe2x80x9coligomericxe2x80x9d).
The fluoroaliphatic group Rf and the fluorine-free aliphatic group are each linked to the organic portion (i.e. the oligomeric backbone or the unsaturated portion of the monomer) by a linking groups designated as Q and Qxe2x80x2 respectively in the Formulas III to VI used herein. Q and Qxe2x80x2 are independently linking groups that may be a covalent bond, divalent alkylene, or a group that can result from the condensation reaction of a nucleophile such as an alcohol, an amine, or a thiol with and electrophile, such as an ester, acid halide, isocyanate, sulfonyl halide, sulfonyl ester, or may result from a displacement reaction between a nucleophile and leaving group. Each Q and Qxe2x80x2 is are independently chosen, preferably contains from 1 to about 20 carbon atoms and can optionally contain catenary oxygen, nitrogen, sulfur, or silicon-containing groups or a combination thereof Q and Qxe2x80x2 is preferably free of functional groups that substantially interfere with free-radical oligomerization (e.g., polymerizable olefinic double bonds, thiols, easily abstracted hydrogen atoms such as cumyl hydrogens, and other such functionality known to those skilled in the art). Examples of suitable linking groups Q and Qxe2x80x2 include straight chain, branched chain, or cyclic alkylene, arylene, aralkylene; oxy, oxo, hydroxy, thio, sulfonyl, sulfoxy, amino, imino, sulfonamido, carboxamido, carbonyloxy, urethanylene, urylene, and combinations thereof such as sulfonamidoalkylene. Preferably linking group Q is a covalent bond or a sulfonamidoalkylene group. Preferably linking group Qxe2x80x2 is a covalent bond.
Suitable linking groups Q and Qxe2x80x2 include the following structures in addition to a covalent bond. For the purposes of this list, each k is independently an integer from 0 to about 20, R1xe2x80x2 is hydrogen, phenyl, or alkyl of 1 to about 4 carbon atoms, and R2xe2x80x2 is alkyl of 1 to about 20 carbon atoms. Each structure is non-directional, i.e. xe2x80x94(CH2)kC(O)Oxe2x80x94 is equivalent to xe2x80x94O(O)C(CH2)kxe2x80x94.
The organic aliphatic moiety, designated R in compounds of Formulas I-VI is a mono-, di-, tri- or tetravalent, linear or branched chain, saturated or unsaturated, cyclic or acyclic (or any combination thereof) organic aliphatic group having from 12 to 75 carbon atoms. In certain embodiments R may be fluorinated (i.e. R =Rf). The valency is equivalent to the value of n in Formula I and is equal to 1 in Formula II. The range of structures contemplated for the organic moiety R will be better understood with reference to the compounds suitable for use in steps of the Reaction Schemes described in detail below. Preferably R is a monovalent alkyl group having from 12 to 75 carbon atoms, preferably 16 to 60 carbon atoms. Where more than one R group is present, such as in Formula II, or when n is greater than one in Formula I, the sum of the carbon atoms in the R groups is preferably from 12 to 100 carbon atoms.
The fluorinated compounds and fluorochemical compositions useful in the invention will be illustrated with reference to the embodiments shown in Formulas I-VI. In such embodiments, linking group L links the fluorochemical oligomeric portion A to the aliphatic group R. Each linking group L may be a covalent bond, a di- or polyvalent alkylene group, or a group that can result from the condensation reaction of a nucleophile such as an alcohol, an amine, or a thiol with an electrophile, such as an ester, acid halide, isocyanate, sulfonyl halide, sulfonyl ester, or may result from a displacement reaction between a nucleophile and leaving group. Each L is independently chosen, preferably contains from 1 to about 20 carbon atoms and can optionally contain catenary (i.e. in-chain) oxygen, nitrogen, sulfur, or silicon-containing groups or a combination thereof, L is preferably free of functional groups that substantially interfere with free-radical oligomerization (e.g., polymerizable olefinic double bonds, thiols, easily abstracted hydrogen atoms such as cumyl hydrogens, and other such detrimental functionalities known to those skilled in the art). Examples of suitable linking groups L include straight chain, branched chain, or cyclic alkylene, arylene, aralkylene, oxy, oxo, sulfonyl, sulfoxy, amino, imino, sulfonamido, carboxamido, carbonyloxy, urethanylene, ureylene, and combinations thereof such as sulfonamidoalkylene. In addition to a covlaent bond, preferred L groups include the following structures (including combinations and multiples thereof) wherein each k is independently an integer from 0 to about 20, R2xe2x80x2 is alkyl of 1 to about 20 carbon atoms.
Returning now to Formulas III to VI above, R1 is hydrogen, halogen (e.g., fluoro, chloro, bromo), or straight chain or branched chain alkyl of 1 to about 4 carbon atoms (e.g., methyl, ethyl, propyl, isopropyl, butyl, isobutyl, and the like). Each R2 is independently hydrogen or straight chain or branched chain alkyl of 1 to about 4 carbon atoms.
X is a group derived from a free-radical initiator. As used herein, the term xe2x80x9cfree-radical initiatorxe2x80x9d designates any of the conventional compounds such as organic azo compounds, organic peroxides (e.g., diacyl peroxides, peroxyesters, dialkyl peroxides) and the like that provide initiating radicals upon homolysis. As used herein, the term xe2x80x9cgroup derived from a free-radical initiatorxe2x80x9d designates an initiating radical formed upon homolytic decomposition of a free-radical initiator.
Suitable groups X include non-reactive groups such as a hydrogen atom, t-butoxy (derived from di-t-butylperoxide), and benzoyloxy (derived from benzoyl peroxide), and reactive groups such as xe2x80x94CCH3(CN)CH2CH2CO2H (derived from azo-4-cyanoisovaleric acid), xe2x80x94C(CH3)2CN (derived from azoisobutyronitrile), and those derived from other known functional azo compounds such as 2,2xe2x80x2-azobis[N-(4-chlorophenyl)-2-methylpropionamidine]-dihydrochloride; 2,2xe2x80x2-azobis[N-(4-hydroxyphenyl)-2-methylpropionamidine]dihydrochloride; 2,2,-azobis[N-(4-aminophenyl)-2-methylpropionamidine]-tetrahydrochloride; 2,2xe2x80x2-azobis[2-methyl-N-2-propenylpropionamidine]dihydrochloride; 2,2xe2x80x2-azobis[N-(2-hydroxyethyl)-2-methylpropionamidine]-dihydrochloride; 2,2xe2x80x2-azobis[2-methyl-N-(2-hydroxyethyl)-propionamide]; 2,2xe2x80x2-azobis[2-(hydroxymethyl)propionitrile]; 2,2xe2x80x2-azobis[2-methyl-N-[1,1-bis(hydroxymethyl)-2-hydroxyethyl]propionamide]; and 2,2xe2x80x2-azobis{2-methyl-N-[1,1-bis(hydroxymethyl)ethyl]-propionamide}. Preferred groups X include those enumerated above.
Surprisingly, it has been found that a strong correlation exists between oil receding contact angle and anti- oil staining properties for fluorochemical oligomers when they are used as leather treatments. Consequently, receding contact angle measurements may be used to readily identify fluorochemical materials having particularly good anti-staining properties, without having to conduct lengthy staining tests on fluorochemical emulsion-treated leather substrates. Compositions having a low receding contact angle measurement generally show poor performance to oil staining. For the purposes of the present invention, fluorochemical oligomers having a receding contact angle to n-hexadecane of at least about 30xc2x0, preferably greater than about 40xc2x0, and more preferably at least about 50xc2x0 are found to exhibit particularly good anti-oil staining properties.
The fluorochemical compounds of Formulas III and V can be prepared by oligomerization of an unsaturated, fluorinated compound (V) in the presence of a free-radical initiator and chain-transfer agent of the formula L(SH)m (m=1-4) according to the following Scheme: 
The fluorochemical compounds of Formulas IV and VI can be prepared by oligomerization of an unsaturated compound having a fluorinated aliphatic pendent group (VII) and an unsaturated compound having a fluorine-free aliphatic pendent group (IX) in the presence of a free-radical initiator and chain-transfer agent of the formula L(SH)m (for m=1) according to the following Scheme: 
The moiety xe2x80x9cLxe2x80x9d corresponds to the linking group moiety L of Formula V or VI.
When the chain-transfer agent contains more than one sulfhydryl group, multiple fluoroaliphatic groups A may be linked through linking groups L to one or more aliphatic R groups. For examples, when the chain transfer agent contains two sulfhydryl groups, two fluoroaliphatic groups A may be linked to L as follows: 
Compounds of Formula (VII) and methods for the preparation thereof are known and disclosed, e.g., in U.S. Pat. Nos. 2,803,615 (Ahlbrecht et al.) and 2,841,573 (Ahlbrecht et al.) which disclosures are incorporated herein by reference. Examples of such compounds include general classes of fluorochemical monomers such as acrylates, methacrylates, vinyl ethers, and allyl compounds containing fluorinated sulfonamido groups, acrylates or methacrylates derived from fluorochemical telomer alcohols, fluorochemical thiols, and the like. Preferred compounds of Formula VII include N-methyl perfluorobotanesulfonamidoethyl acrylate, N-methyl perfluorooctanesulfonamidoethyl methacrylate, N-ethyl perfluorooctanesulfonamidoethyl acrylate, N-ethyl perfluorohexylsulfonamidoethyl methacrylate, the reaction product of isocyanatoethyl methacrylate and N-methylperfluorooctanesulfonamidoethyl alcohol, 1,1-dihydroperfluorooctyl acrylate, N-methyl perfluorooctanesulfonamidoethyl vinyl ether, C4F9SO2NHCH2CHxe2x95x90CH2, and others such as perfluorocyclohexyl acrylate (c-C6F11CH2OCOCHxe2x95x90CH2), and tetrameric hexafluoropropyleneoxide dihydroacrylate.
Compounds of Formula IX may be selected from alkyl acrylate esters, vinyl acetate, styrene, alkyl vinyl ethers, alkyl methacrylate esters, acrylic acid, methacrylic acid, acrylamide, methacrylamide, acrylonitrile, methacrylonitrile, and N-vinylpyrrolidone. Alkyl acrylate ester monomers useful in the invention include straight-chain, cyclic, and branched-chain isomers of alkyl esters containing C1-C50 alkyl groups. Useful specific examples of alkyl acrylate esters include: methyl acrylate, ethyl acrylate, n-propyl acrylate, 2-butyl acrylate, iso-amyl acrylate, n-hexyl acrylate, heptyl acrylate, n-octyl acrylate, iso-octyl acrylate, 2-ethylhexyl acrylate, nonyl acrylate, decyl acrylate, undecyl acrylate, dodecyl acrylate, tridecyl acrylate, and tetradecyl acrylate.
When the chain transfer agent L(SH)m bears a functional group, a compound of Formula VIII (Scheme I) or Formula X (Scheme 2) may be further reacted with a functional aliphatic compound to form the linking group L and incorporate the R group into the compounds of Formulas I, II and V or VI. The nature of the functional groups on both the chain transfer agent and the aliphatic compounds are chosen so that they are reactive toward one another to form the L linking group. Examples of mutually reactive pairs include an acyl group (such as a carboxylic acid, acyl halide or ester) reacting with an alcohol or amine, an alcohol or an amine reacting with a xe2x80x9cleaving groupxe2x80x9d such as a halide or tosylate, and an isocyanate reacting with an alcohol or amine.
A compound of Formulas VIII or X may be provided with functional groups on the L linking group (in addition to the sulfhydryl group(s)) through the use of an appropriate functionalized chain-transfer agent L(SH)m, wherein L contains a functional group. Suitable functional groups for inclusion in the chain-transfer agent include hydroxy, amino, halo, epoxy, haloformyl, aziridinyl, acid groups and salts thereof, which react with an electrophile or nucleophile, or are capable of further transformation into such groups. The use of a functionalized chain-transfer agent allows for subsequent incorporation of the xe2x80x9cRxe2x80x9d group of Formulas I and II, and V or VI. For example, the xe2x80x9cLxe2x80x9d group of the chain transfer agent may be substituted with an electrophilic ester moiety. This ester moiety will allow incorporation of a long chain xe2x80x9cRxe2x80x9d group by further reaction with an aliphatic alcohol having a nucleophilic hydroxyl group. Reaction between the two moieties produces an ester linkage, thereby linking the fluorochemical oligomeric moiety A with the aliphatic moiety R. Alternatively, for example, the L moiety may be substituted with a hydroxyl group that may be reacted with an aliphatic ester to link the fluorochemical oligomeric moiety A with the aliphatic moiety R.
Examples of such functionalized chain transfer agents include 2-mercaptoethanol, mercaptoacetic acid, 2-mercaptobenzimidazole, 2-mercaptobenzoic acid, 2-mercaptobenzothiazole, 2-mercaptobenzoxazole, 3-mercapto-2-butanol, 2-mercaptosulfonic acid, 2-mercaptonicotinic acid, 4-hydroxythiopheno-3-mercapto-1,2-propanediol, 1-mercapto-2-propanol, 2-mercaptopropionic acid, N-(2-mercaptopropionyl)glycine, 3-mercaptopropyltrimethoxysilane, 2-mercaptopyridine, 2-mercaptopyridine-N-oxide, 2-mercaptopyridinol, mercaptosuccinic acid, 2,3-mercaptopropanesulfonic acid, 2,3-dimercaptopropanol, 2,3-dimercaptosuccinic acid, cystine, cystine hydrochloride, cystine ethylester. Preferred functionalized chain-transfer agents include 2-mercaptoethanol, 3-mercapto-1,2-propanediol, 4-mercaptobutanol, 11-mercaptoundecanol, mercaptoacetic acid, 3-mercaptopropionic acid, 12-mercaptododecanoic acid, 2-mercaptoethylamine, 1-chloro-6-mercapto-4-oxahexan-2-ol, 2,3-dimercaptosuccinic acid, 2,3-dimercaptopropanol, 3-mercaptopropyltrimethoxysilane, 2-chloroethanethiol, 2-amino-3-mercaptopropionic acid, and compounds such as the adduct of 2-mercaptoethylamine and caprolactam.
Advantageously, the R group of Formulas I, II, V or VI may be incorporated by use of a non-functional chain transfer agents. Non-functionalized chain-transfer agents are those that contain a group capable of terminating a radical chain reaction (e.g., a sulfhydryl) but no further functional groups capable of reacting with nucleophiles, electrophiles, or capable of undergoing displacement reactions. In such cases, the aliphatic portion of L(SH)n provides the aliphatic group R of Formulas I, II and V or VI. Such compounds include mono, di, and polythiols such as ethanethiol, propanethiol, butanethiol, hexanethiol, n-octylthiol, t-dodecylthiol, 2-mercaptoethyl ether, 2-mercaptoimidazole, 2-mercaptoethylsulfide, 2-mercaptoimidazole, 8-mercaptomenthone, 2,5-dimercapto-1,3,4-thiadiazole, 3,4-toluenedithiol, o-, m-, and p-thiocresol, ethylcyclohexanedithiol, p-menthane-2,9-dithiol, 1,2-ethanedithiol, 2-mercaptopyrimidine, and the like. Longer chain alkyl thiols having 12 to 75 carbon atoms being preferred.
Whether functionalized or not, a chain transfer agent is present in an amount sufficient to control the number of polymerized monomer units in the oligomer. The end-capping agent is generally used in an amount of about 0.05 to about 0.5 equivalents, preferably about 0.25 equivalents, per equivalent of olefinic monomers VII and/or IX.
Also present in oligomerization process is a free-radical initiator as defined above in connection with X. Such compounds are known to those skilled in the art and include persulfates, azo compounds such as azoisobutyronitrile and azo-2-cyanovaleric acid and the like, hydroperoxides such as cumene, t-butyl, and t-amyl hydroperoxide, dialkyl peroxides such as di-t-butyl and dicumyl peroxide, peroxyesters such as t-butyl perbenzoate and di-t-butylperoxy phthalate, diacylperoxides such as benzoyl peroxide and lauroyl peroxide.
The initiating radical formed by an initiator can be incorporated into the fluorochemical oligomer to varying degrees depending on the type and amount of initiator used. A suitable amount of initiator depends on the particular initiator and other reactants being used. About 0.1 percent to about 5 percent, preferably about 0.1 percent, to about 0.8 percent, and most preferably about 0.2 percent to 0.5 percent by weight of an initiator can be used, based on the total weight of all other reactants in the reaction.
The oligomerization reaction of Schemes 1, 2 and 3 can be carried out in any solvent suitable for organic free-radical reactions. The reactants can be present in the solvent at any suitable concentration, e.g., from about 5 percent to about 90 percent by weight based on the total weight of the reaction mixture. Examples of suitable solvents include aliphatic and alicyclic hydrocarbons (e.g., hexane, heptane, cyclohexane), aromatic solvents (e.g., benzene, toluene, xylene), ethers (e.g., diethylether, glyme, diglyme, diisopropyl ether), esters (e.g., ethyl acetate, butyl acetate), alcohols (e.g., ethanol, isopropyl alcohol), ketones (e.g., acetone, methyl ethyl ketone, methyl isobutyl ketone), sulfoxides (e.g., dimethyl sulfoxide), amides (e.g., N,N-dimethylformamide, N,N-dimethylacetamide), halogenated solvents such as methylchloroform, FREON(trademark) 113, trichloroethylene, xcex1,xcex1,xcex1,-trifluorotoluene, fluorinated ethers such as C4F9OCH3 and the like, and mixtures thereof.
The oligomerization can be carried out at any temperature suitable for conducting an organic free-radical reaction. Particular temperature and solvents for use can be easily selected by those skilled in the art based on considerations such as the solubility of reagents, the temperature required for the use of a particular initiator, and the like. While it is not practical to enumerate a particular temperature suitable for all initiators and all solvents, generally suitable temperatures are between about 30xc2x0 C. and about 200xc2x0 C.
Useful fibrous substrates which may be topically treated (surface treated) include natural textiles and fabrics such as cotton or wool and synthetic fabrics or textiles such as polyester or nylon, as well as paper and leather. Topical treatment can be done via immersion, spray, foam, kiss roll and metering. For example, the substrate can be immersed in a dispersion or solution of the fluorochemical oligomer and agitated until it is saturated. The saturated substrate can then be run through a padder/roller to remove excess dispersion, dried in an oven at a relatively low temperature (e.g., 70xc2x0 C.) for a time sufficient to remove the dispersion medium (e.g. solvents such as those used in the oligomerization reaction), and cured at a temperature and for a time sufficient to provide a cured treated substrate. This curing process can be carried out at temperatures between ambient temperature and about 150xc2x0 C. depending on the particular composition used. In general, a temperature of about 40 to 150xc2x0 C. for a period of about 10 minutes is suitable. The cured treated substrate can be cooled to room temperature and used as desired, e.g., incorporated or fashioned into a garment such as rainwear.
A fluorochemical oligomer in connection with the present invention is preferably used as an aqueous composition, in particular an aqueous dispersion in water. If the oligomer is made by solution polymerization, it can be dispersed in water, through vigorously mixing the solution oligomer with water. A solvent free dispersion can be obtained by subsequent distillation of the oligomerization solvent. In accordance with a preferred method of treating leather in connection with this invention, a leather such as a tanned hide is contacted with an aqueous composition, preferably an aqueous dispersion, comprising amphiphilic copolymer. Aqueous dispersions in accordance with the invention are suitable for the treatment of all conventional tanned hides, in particular hides tanned with mineral tanning agents, such as chromium(III), aluminum or zirconium salts. The tanned hides are usually neutralized before treatment, and may be dyed before treatment. However, dyeing may also be carried out after a waterproofing treatment in accordance with this invention.
The tanned hides can be treated with an aqueous dispersion comprising an oligomer in accordance with the invention preferably in an aqueous liquor obtained by diluting the oligomeric dispersions with water, at a pH of from 3 to 10, preferably from 5 to 8, and at from 20xc2x0 C. to 70xc2x0 C., preferably from 40xc2x0 C. to 60xc2x0 C. The amount of the oligomer dispersion applied to the leather in accordance with this invention is chosen so that sufficiently high or desirable water repellency is imparted to the substrate, said amount usually being between 0.1% and 30% by weight, preferably between 0.5% and 15% by weight, based on the shaved weight of the leather or the wet weight of the hide or wet blue leather. The amount which is sufficient to impart desired repellency can be determined empirically and can be increased as necessary or desired. The treatment is effected, for example, by drumming. After the treatment with the aqueous dispersion described above, the pH of the treatment liquor is preferably brought to 3-5, preferably 3.3-4, by addition of an acid in particular an organic acid, such as formic acid.
The amount of the fluorochemical composition applied to a substrate in accordance with this invention is chosen so that sufficiently high or desirable water and oil repellencies are imparted to the substrate surface, said amount usually being such that 0.01% to 5% by weight, preferably 0.05 to 2% by weight, of fluorine is present on the treated substrate. The amount which is sufficient to impart desired repellency can be determined empirically and can be increased as necessary or desired.
To prepare the aqueous dispersions, the oligomers, together with cationic or anionic and, if appropriate, nonionic dispersing and/or emulsifying or surfactant agents and, if appropriate, other auxiliaries and solvents, are vigorously dispersed in water, a relatively large amount of energy being supplied. To facilitate the preparation of the dispersion, the oligomer product may be dissolved first in solvent or mixture of solvents, and the dispersion is advantageously carried out in two separate steps, predispersion being carried out first, followed by fine dispersion. Predispersion can also be carried out by using high shearing forces, for example by using a high-speed stirrer, such as a dispersing machine of the Ultraturax(trademark) type, and the predispersion thereby obtained is then subjected, for example, to ultrasonic treatment or treatment in a high pressure homogenizer. After this treatment, the particle size in the dispersion generally will be equal to or less than 1 (mu)m to the extent of more than 80%, preferably to the extent of more than 95%. Generally, the aqueous dispersion as a concentrate contains 5 to 50% by weight of an active composition (oligomers), 0.5 to 15% by weight of one or more dispersing and/or emulsifying agents, and 0 to 30% by weight of a solvent or solvent mixture, the remainder being water. Solventless dispersions can be prepared by removing the solvent by distillation.
Mixtures of water-insoluble solvents with water-soluble solvents can be employed as the solvent for preparation of the dispersion, the amount of the water-insoluble solvent in most cases being greater than the water-soluble solvent. Suitable water-soluble solvents are, for example, mono- or di-alcohols, lower ketones, polyglycol esters, and polyglycol ethers, or mixtures of such solvents. Examples of water-insoluble solvents are esters, ethers, and higher ketones. Low-boiling solvent portions can be removed by, for example, distillation, at a later time, if desired. Preferred water-insoluble solvents are esters or ketones, such as ethyl acetate, butyl acetate, and methyl ethyl ketone.
In order to increase repellency properties and the durability thereof and to aid in the application of an aqueous composition according to the present invention to a leather substrate to be treated therewith, it may be advantageous to incorporate into an aqueous composition according to this invention, one or more other substances such as oil and/or water repellent compositions and/or siloxane softening agents. Also other additives such as conventional leather finishing agents e.g. retanning, fatliquoring agents can be added.
Further suitable water and/or oil repellent composition that can be used in connection with this invention comprise polysiloxanes having fluoroaliphatic- and carboxyl-containing terminal groups as disclosed in WO 94/12561, fluoro- and polysiloxane- containing urethanes as disclosed in EP 298364, carboxyl group containing polysiloxanes as disclosed in EP 324345. Still further water and/or oil repellent compositions are disclosed in U.S. Pat. Nos. 4,525,305, 4,920,190, 4,782,175, 4,778,915, 4,539,006, 3,923,715 and 4,709,074.